In semiconductor chip fabrication operations, it is crucial that temperature, air pressure, and humidity conditions be maintained precisely. A slight variation in any of these environmental factors can have detrimental effects on the fabrication process.
Dry air is particularly troublesome. Not only is a precise humidity level required for the fabrication process, but also, dry air has other adverse effects, such as drawing moisture out of materials and contributing to the generation of static electricity. These potential problems make controlling the level of humidity extremely important.
Many chip fabrication and clean room operations are equipped with steam humidifiers installed in the air supply or ventilation systems. However, there are a number of problems and disadvantages with these humidifying systems. One common problem is that they humidify the ambient air unevenly. That is, some humidifiers produce a non-uniform absorption and mixing of water vapor into the ambient air stream. If too much vapor is introduced by the humidifier, the excess amount is not absorbed by the air stream. The excess amount condenses on virtually any surface it contacts. Obviously, this is an unacceptable problem in semiconductor manufacturing operations, where a pristine environment is required.
The most relevant prior art that relates to the above problem is the Vaporstream.RTM. Model "D.I." humidifier manufactured by Dri-Steem Humidifier Company. This humidifier features an external, stainless steel, vapor dispersion tube with a plurality of holes, arranged so that multiple jets of steam or vapor coming out of the holes are introduced into the ambient air stream. By introducing multiple jets of steam into the air stream in this manner, the Dri-Steem humidifier claims to produce an improvement in the rate and thoroughness of vapor absorption. Dri-Steem's tube design also allows any condensate which forms on the interior of the tube to flow back to the humidifier.
The present invention is a humidifier that differs significantly from the prior art in that it utilizes structures placed within the humidifier's water reservoir to uniformly control the generation of steam, as opposed to using a multiple-holed dispersion tube located outside of the humidifier reservoir. How the invention works is further described below.